747-8 Assumed Temp Reduction?

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Hi everyone, I'm pretty happy flying with the new PMDG 747-8 V3, but right now applications like TOPCAT and TOPER are not able to calculate Assumed Temp Reduction for the 747-8 yet and I don't know when there will be an update for it. I also tried to use the EFB on the 748 but it says that this feature will not be available until PMDG releases an update. So there's the problem, I am not able to calculate the assumed temp reduction. I asked some people around and they said that I can use something like this 👇 to calculate, but I really don't get it, so can anyone explain it to me how it works, or give me some other suggestions on this problem? Thanks!

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Hi everyone, I'm pretty happy flying with the new PMDG 747-8 V3, but right now applications like TOPCAT and TOPER are not able to calculate Assumed Temp Reduction for the 747-8 yet and I don't know when there will be an update for it. I also tried to use the EFB on the 748 but it says that this feature will not be available until PMDG releases an update. So there's the problem, I am not able to calculate the assumed temp reduction. I asked some people around and they said that I can use something like this 👇 to calculate, but I really don't get it, so can anyone explain it to me how it works, or give me some other suggestions on this problem? Thanks!

Lets consider the runway you are going to takeoff is 3600m long and the outside air temperature at your origin airport is 22ºC. The limiting weight for this condition is 438500kg (just cross the runway lenght line with OAT column).
Now lets say your takeoff gross weight is 410000kg. So you take the runway lenght line to the right all the way to 411500kg (as the next one is less then your expected TOGW) and you'll notice the OAT column is 38ºC. So this is the temperature limit for your weight, with flaps 10 at sea level, packs on, anti-ice off, dry runway. Of course you have to adjust for different conditions (and there are many other things you have to consider as well), as depicted on the charts. But for simulation pourposes, you can go with 38ºC assumed temperature at sea level, flaps 10 takeoff.

Edited September 28 by MauB

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Here is the workaroun at the moment. This is a perfectly legitimate way to get an assumed temperature. Albeit, it might not take into account obstacles, but then neither does TOPER. I doubt PMDG has obstacles in the EFB database. Not something to worry too much about in the FS world anyway.

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Obstacle information for a runway can be added in the EFB by creating a temporary NOTAM (see EFB manual page 82). This will allow you to define one obstacle. If you want to add many obstacles you can "overwrite" the runway data by creating a new temporary airport (see EFB manual page 78).

For my assumed temperature I look at the same line for the higher temperatures, and see that even at 50°C I´m way below the Field & climb limit weight, so I can use an assumed temperature of 50° (and probaly higher, but I got no figures for that).

Had my TOGW been 800.000 LB ( 362.874 kg) then the max assumed temperature would have been 38°C

Had the runway been Wet, then I had to use the tables starting from page 324 (PD20.8).

Also if the airport had been at higher altitude, tables for these are on page 319-323 (PD20.3-20.7). The altitude tables comes in steps of 0, 2.000, 4.000, 6.000, 8.000 and 10.000 ft.

Use interpolation where adequitein all tables. In my opinion You can use closets guestimate instead of detailed interpolation, since in the end it´s only "in the ballpark" figures anyway - simply use closest safe figures.

FinnJ

Edited September 29 by Wothan

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As i detailed in the other post you can just use the EFB with your actual take off weight guestimating temperatures until you find the highest temperature you can depart at without a exceeded max warning...

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